Powershift synchronized transmission

ABSTRACT

Disclosed is a power shift transmission having torque converter, an input shaft driven by the torque converter, a countershaft in continuous driving relation with the input shaft, an output shaft having first, second, and third speed ratios journaled thereon and driven via the countershaft, a reverse speed ratio gear splined to the output shaft and driven via a gear on an idler shaft driven by the countershaft, a first friction clutch mechanism for connecting the first speed ratio gear to the output shaft, a second friction clutch mechanism for connecting the output shaft directly to the input shaft, a blocker-clutch assembly for coupling the second and third speed ratio gears to the output shaft, and an actuator assembly for shifting the blocker-clutch assembly into and out of coupling engagement. The friction clutches are momentarily engageable to relieve driving and coast mode torque on the blocker-clutch and to synchronize the blocker-clutch. An alternative embodiment of the transmission includes a torque converter driven shaft for driving the countershaft and a torque converter bypass shaft which is connected directly to the output shaft via the second friction clutch mechanism.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to copending U.S. applications Ser. Nos.973,262, filed Dec. 26, 1978; 973,266, filed Dec. 26, 1978; 973,267,filed Dec. 26, 1978; and 973,270, filed Dec. 26, 1978. All of theseapplications are assigned to the assignee of this application.

FIELD OF THE INVENTION

This invention relates to transmissions and, more specifically, totransmissions which are powershifted and synchronized.

BACKGROUND OF THE INVENTION

It is known in the art to selectively engage and disengage positive orjaw type clutches to shift a transmission from one speed ratio toanother. Positive clutches are preferred in transmissions since they arecompact and inexpensive relative to friction clutches and are extremelyreliable if they are synchronously engaged. Most of these transmissionsare manually shifted and employ a manually operated friction clutch fordisconnecting the transmission input shaft from a prime mover whenshifting from one ratio to another. Such disconnecting by the frictionclutch has the disadvantage of interrupting the driving connectionbetween the prime mover and the load connected to the transmissionoutput shaft. Further, when such transmissions are used in relativelyheavy vehicles, the vehicle operator must perform a double clutchingmanipulation of the friction clutch when shifting from one ratio toanother. When double clutching, the operator must momentarily disengagethe friction clutch to relieve torque on the positive clutch to bedisengaged, then momentarily reengage the friction clutch to synchronizethe positive clutch to be engaged, and then momentarily disengage thefriction clutch prior to engagement of the positive clutch to minimizeshock loading. Further, when the friction clutch is momentarilyreengaged, the vehicle operator must either increase or decrease theprime mover speed to bring the positive clutch to synchronism. If theoperator is unskilled or if the vehicle is moving slowly and/or if thevehicle is on a steep grade, it is not uncommon for a shift to be missedor for the positive clutches to be abused due to asynchronousengagement.

Many attempts have been made to adapt the above type of transmissions toautomatic or semiautomatic controls to negate the above problems. Onesuch attempt, as disclosed in U.S. Pat. No. 3,589,483, proposes positiveclutches for engaging the several speed ratios, a first friction clutchfor connecting the several speed ratio gears to a prime mover, a secondfriction clutch for connecting the transmission output shaft directly tothe prime mover and synchronizing the positive clutches duringupshifting, and a semiautomatic control system for controlling thesequential operation of the friction and positive clutches when a shiftcontrol lever is moved from one ratio position to another. When thelever is moved in an upshift sense, the control automatically providespower upshifting and synchronizing by momentarily or partiallydisengaging the first friction clutch and by momentarily or partiallyengaging the second friction clutch. When the lever is moved in adownshift sense, the control automatically provides a partial powerdownshifting by manipulating engagement and disengagement of thefriction clutches, but synchronizing must be provided by engine speedmanipulation. During both upshifting and downshifting, the clutch teethof the positive clutch to be engaged are moved into abutment with eachother prior to synchronism therebetween, thereby exposing the positiveclutches to asynchronous engagement.

SUMMARY OF THE INVENTION

An object of this invention is to provide a ratio change transmissionemploying both friction and positive type clutches to engage thedifferent ratios and further employing the friction clutches whenupshifting and downshifting into at least one positive clutch tomaintain a driving connection through the transmission and tosynchronize the positive clutch.

According to a feature of the invention, the transmission includes aninput shaft and an output shaft and at least one countershaft and ratiochange means operative to provide at least low, intermediate, and highspeed ratio changes between the input and output shafts via thecountershaft; the ratio change means includes a low and an intermediatespeed ratio gear mounted for rotation about one of the shafts, first andsecond jaw clutch members operative when engaged to couple theintermediate gear to the one shaft and to provide the intermediate speedratio, a first friction clutch fully engageable to couple the low gearto the one shaft and to provide the low speed ratio and momentarilyengageable during downshifting into the intermediate speed ratio tosynchronize the jaw clutch members, and a second friction clutch fullyengageable to couple the input shaft directly to the output shaft toprovide the high speed ratio and momentarily engageable duringupshifting into the intermediate speed ratio to synchronize the jawclutch members.

BRIEF DESCRIPTION OF THE DRAWINGS

The transmission of the instant invention is shown in the accompanyingdrawings in which:

FIG. 1 is a partially sectioned view of the transmission, looking alongline 1--1 of FIG. 2;

FIG. 2 is an end view of the rear housing member of the transmission;

FIG. 3 is a partially sectioned view of a torque converter shown in FIG.1;

FIG. 4 is a fully sectioned view of a portion of the transmission ratiogearing, clutches, and an actuator;

FIGS. 4A and 4B are detailed views of a portion of a blocker-clutch inFIG. 4;

FIG. 5 is a fully sectioned view of another portion of the transmissionratio gearing, clutches, and an acutator; and

FIG. 6 is an alternative embodiment of the transmission torque converterand input shaft.

DETAILED DESCRIPTION OF THE DRAWINGS

Looking now at FIGS. 1 and 2 and in particular FIG. 1, therein is showna powershift transmission 10, partially sectioned along line 1--1 ofFIG. 2. The transmission is intended for use in a land vehicle but isnot limited to such use. The transmission is preferably automaticallyshifted by an unshown control system which forms no part of the instantinvention. The transmission includes a housing assembly 12, a fluidcoupling or torque converter assembly 14 which may be directly driven byan unshown internal combustion engine, an input shaft 16, an outputshaft assembly 18 including an output shaft 20, at least onecountershaft assembly 22 including countershaft members 24 and 26splined together at 27, a friction clutch assembly 28, a blocker-clutchassembly 30, an actuator assembly 32, and a reverse gear assembly 34including an idler shaft 36.

In describing transmission 10, its leftward portion, as shown in FIG. 1,will be referred to as the front and its rightward portion will bereferred to as the rear.

Housing assembly 12 includes a front housing member 38, having a bellhousing portion 38a integrally formed therewith, a rear housing member40, and an intermediate plate member 42. Members 38, 40, and 42 aresecured together via a plurality of bolts 43. A flange portion 38b ofbell housing 38a provides means for securing the transmission to therear of an unshown engine. The front housing member carries bearings 44and 46 for rotatably supporting input shaft 16 and countershaft 24. Therear housing member carries bearings 48, 50, and 52 for rotatablysupporting output shaft 20, countershaft 26, and idler shaft 36. Lookingat both FIGS. 1 and 2, the true position of countershaft 26, idler shaft36, and actuator assembly 30, relative to output shaft 20, may begleaned from the position of bosses 40a and 40b which carry bearings 50and 52 and from a boss 40c which defines a portion of a cylinder housing54 of the actuator assembly 32. Intermediate plate 42 includes a throughbore 42a for the passage of output shaft 20 and through bores 42b and42c which carry bearings 56 and 58 for rotatably supporting countershaft26 and idler shaft 36. Rear housing member 40 further includes a powertakeoff pad 40d and a flange 40e for the attachment of an oil pan 60,shown only in FIG. 2.

Looking now at FIGS. 1 and 3 and in particular FIG. 3, torque converterassembly 14 includes an impeller 62 driven by a shroud 64, a turbine 65hydraulically driven by the impeller and in turn drivingly fixed toinput shaft 16 at 66, and a runner or stator 68 which becomes groundedto housing member 38 via a one-way roller clutch 70 carried by a sleeve72 fixed to the housing member. The rear side of shroud 64 is fixed to asleeve 74 which rotatably supports the rear of the shroud and drives apump 76. Pump 76 may be a well known crescent gear pump for pressurizingthe torque converter, for lubricating the transmission, and forproviding pressurized fluid to engage friction clutches and actuators inthe transmission.

Looking now at FIGS. 1 and 4 and in particular FIG. 4, input shaft 16 isintegrally formed with an input gear 16a which is in constant mesh witha countershaft gear 78, an annular flange 16b for connecting the inputshaft to friction clutch assembly 28, and a recess 16c carrying abearing 80 for rotatably supporting the front end of output shaft 20.Friction clutch assembly 28 includes a clutch mechanism 82 forconnecting the input shaft directly to the output shaft and a clutchmechanism 84 for connecting a low or first speed ratio gear 86, drivenby the countershaft, to the output shaft.

Clutch mechanism 82 includes a housing member 88 splined to shaft 20, aset of friction disks 90 slideably splined to internal splines 88adefined by member 88, a set of friction disks 92 slideably splined toexternal splines 16d defined by annular flange 16b, a piston 94 forsqueezing the disks together in response to pressurized fluid beingintroduced into a chamber 96 defined by housing member 88 and piston 94,and a set of return springs 98 for retracting the piston. Housing member88 is axially retained by a shoulder 20a defined by a step in shaft 20and a snap ring 100 which also retains a radially extending flange 102having springs 98 reacting thereagainst. Pressurized oil for actuatingclutch 82 is introduced into chamber 96 via a passage 104 in housing 88,passages 106, 108, and 110 in shaft 20, and passages 112 and 114 inintermediate plate 42 and in an annular rim portion 42d which extendsthe axial interface of bore 42a with shaft 20. Passage 114 is connectedto an unshown control system which is selectively operative to providethe pressurized oil. Passages 108 and 114 are sealed at their forwardand rearward ends, respectively, by interference fit balls 116 and 118.Passages 104 and 106 are sealed at their respective interface withmember 88 and bore 42a via pairs of seals 105 and 107. Oil forlubricating bearing 80 and the disks of clutch 82 flows through apassage 120 in intermediate plate 42, passages 122, 124, and 126 inshaft 20, and a plurality of passages 128 in flange 16b. Passage 124 issealed at its forward end by an interference fit ball 127.

Clutch mechanism 84 includes a housing member 130 rotatably supported onshaft 20 via a bearing 132, a set of friction disks 134 slideablysplined to internal splines 130a defined by member 130, a set of disks136 slideably splined to external splines 88b defined by housing member88, a piston 138 for squeezing the disks together in response topressurized oil being introduced into a chamber 140 defined by housingmember 130 and piston 138, a set of return springs 142 for retractingthe piston, and a hub portion 130b defined by housing member 130. Lowratio gear 86 is splined to hub portion 130b and axially retainedthereon by a snap ring 141. Housing member 130 is axially retained forrotation relative to housing member 88 and rim portion 42d via thrustbearings 144 and 146. Springs 142 react against a radially extendingflange 148 secured to member 130 via a snap ring 150. Pressurized oilfor actuating clutch 84 is introduced into chamber 140 via passages 152and 154 in hub portion 130b and passages 156 and 158 in rim portion 42dand intermediate plate 42. Passage 156 is sealed at its interface withhub portion 130b via a pair of seals 160. Passage 158 is sealed at itsrearward end by an interference fit ball 162. Oil for lubricatingbearings 132, 144, and 146 and the disks of clutch mechanism 84 flowsthrough passages 124, 164, and 166. Passage 158 is connected to theunshown control system which is selectively operative to provide thepressurized oil.

Looking now in the area of blocker-clutch mechanism 30, therein arethree gears, a reverse speed ratio gear 168 splined to shaft 20 andretained against forward movement by a shoulder 20b and first and secondintermediate speed ratio gears 170 and 172 supported for rotation onshaft 20 by sleeve bearings 174 and 176. Gears 170 and 172 each includean axially extending sleeve portion or jaw clutch member 170a and 172awhich each have external jaw clutch splines 170b and 172b. Gears 170 and172 are axially spaced apart by a sleeve 178 splined on its I.D. toshaft 20 and retained against axial movement by a shoulder 20c and asnap ring 180. Gears 170 and 172 are axially retained on their forwardand rearward sides, respectively, by thrust bearings 182 and 184.

Blocker-clutch mechanism 30 includes the jaw clutch members 170a and172a, a jaw clutch member or means 186 having internal jaw clutchsplines 186a slideably splined to external splines on sleeve 178, aradially extending flange portion 186b integrally formed with member186, three circumferentially positioned pins 188 (one of which is shown)extending parallel to the axis of shaft 20 and through holes 186c inflange portion 186b, two friction cone-clutch members 190 and 192rigidly secured together by pins 188, two friction cone-clutch members170c and 194 engageable with friction members 190 and 192 and each fixedfor rotation with its respective gear, and three circumferentiallypositioned split pins 196 (one of which is shown) alternately spacedbetween pins 188 and extending parallel to the shaft 20 and throughchamfered holes 186d in flange portion 186b.

Looking momentarily at both FIGS. 4 and 4A, each split pin includes apair of semicylindrical halves 198 and 200 having a major diameter lessthan the I.D. of holes 186d when squeezed together, semiannular grooves198a, and 200a with chamfered ends, and a leaf spring 202 for biasingthe annular grooves apart to engage the groove chamfers with the holechamfers. Halves 198 and 200 abut at their ends against end walls 190aand 192a of blind bores in friction members 190 and 192.

Looking momentarily at both FIGS. 4 and 4B, each hole 186c extendsparallel to the axis of shaft 20 and includes oppositely facing squareshoulders 186e and 186f positioned normal to the axis of shaft 20. Eachpin 188 includes a major diameter 188a less than the I.D. of itsrespective hole 186c and a groove or reduced diameter portion 188bdefining oppositely facing blocking shoulders 188c and 188d which areparallel to square shoulders 186e and 186f.

When blocker-clutch mechanism 30 is in the disengaged or neutralposition, as shown, gears 170 and 172 are free to rotate relative toshaft 20. When it is desired to couple either gear to the shaft,actuator assembly 32 applies an actuating or engaging force to flangeportion 186b to effect movement of jaw clutch member 186 toward the jawclutch members 170a or 172a. If the engaging force is to the left,initial movement of the flange portion is transmitted through split pins196 via leaf spring 202 and the chamfered shoulders to effect resilientengagement of friction members 190 and 170c. This resilient engagement(provided gear 170 and shaft 20 are rotating asynchronously) causes thereduced diameter portion 188b of pins 188 to move to one side of holes186c, whereby square shoulders 186e engage blocking shoulders 188c toblock engagement of jaw clutch member 186 with jaw clutch member 170auntil gear 170 crosses synchronism with shaft 20. Since shoulders 186eand 188c are normal to the axis of shaft 20 and the direction ofmovement of jaw clutch member 186, the shoulders provide a positive orinfinite block which is independent of the forces on the shoulders andthe frictional torque between friction clutch members 190 and 170c,thereby preventing asynchronous engagement of the jaw clutch membersshould the design frictional torque between the friction members be slowin developing due to oil on the friction surfaces or should the designfrictional torque fade due to a change in the coefficient friction ofthe surfaces.

Actuator assembly 32 includes a hydraulic actuator 204 and a spring box206. Actuator 204 includes the cylinder housing 54 defined by rearhousing member 40, cylindrical bore portions 208a, 208b, 208c, and 208ddefined by a stepped bore 208 having shoulders 208e, 208f, and 208g, anend wall 210 abutting shoulder 208e and retained thereagainst by a snapring 212, a piston rod 214 disposed in bore 208 for sliding movementparallel to the axis of shaft 20 and radially spaced therefrom, a piston215 integrally formed with the piston rod for sliding movement in boreportion 208c, a piston 216 disposed for sliding movement within boreportion 208b and on piston rod 214, and a sleeve or stop member 217slideably supported by piston rod 214 and interposed between thepistons. Piston rod 214 includes an end portion 214a slideably disposedin bore portion 208d for support purposes and an end portion 214bextending through end wall 210. Pistons 215 and 216 divide bore portions208b and 208c into three fluid chambers. The mutually facing sides 215aand 216a of the pistons in part define a first fluid chamber 218 and thedistal sides 215b and 216b of the pistons in part define second andthird fluid chambers 220 and 222. Passages 224, 226, and 228 providemeans for porting oil to and from the fluid chambers via the unshowncontrol system. Conventional seals prevent oil leakage of the cylinderand by the pistons. The seals may be Quad-X Brand Seals obtainable fromMinnesota Rubber Company.

Spring box 206 includes a sleeve 230 concentric to end portion 214b ofthe piston rod 214, annular bearing rings 232 and 234 slideablysupporting the sleeve on the end portion, snap rings 236, 238, 240 and242 defining stop means, a pre-loaded coil spring 244 interposed betweenthe bearing rings and biasing the rings apart and into engagement withthe stop means defined by the snap rings, and a shift fork 230aintegrally formed with the sleeve. Shift fork 230a extends outwardaround the periphery of flange portion 186b and connects the flangeportion to the sleeve in a conventional manner, as may be seen inFIG. 1. Bearing rings 232 and 234 are spaced apart as far as practicableto minimize shift fork cocking forces between the sleeve and endportion. Further, each ring includes concentric sleeve portions, such assleeves 232a and 232b, which define an annular recess for receiving thespring ends and for increasing the outer and inner circumferentialbearing surface of the rings, thereby lowering the surface forces on thebearings to reduce wear.

Looking now at FIGS. 1 and 5 and in particular FIG. 5, countershaftassembly 22 includes the countershaft members 24 and 26, the gear 78fixed for rotation with shaft 24 and in constant mesh with input gear16a, the splined connection 27 connecting shaft 24 to shaft 26, gears246, 248, and 250 fixed for rotation with shaft 26 and in constant meshwith gears 86, 170, and 172, respectively, and a power take-off gear 252also fixed for rotation with shaft 26.

Reverse gear assembly 34 includes the idler shaft 36, a gear 254supported for rotation about shaft 36 via a sleeve bearing 256 and inconstant mesh with gear 248, a gear 258 fixed for rotation with shaft 36and in constant mesh with the reverse speed ratio gear 168 when shaft 36is in its true position as described in connection with housing assembly12 and FIG. 2, a positive clutch assembly 260 for coupling gear 254 withshaft 36, and a hydraulic actuator 262 for selectively moving the clutchinto and out of engagement.

Positive clutch 260 includes a set of jaw clutch teeth 254a defined bygear 254, a jaw clutch member 264 slideably splined to shaft 36, a setof jaw clutch teeth 264a defined by member 264 and engageable with teeth254a, and an annular groove 264b which receives a shift fork 266.

Hydraulic actuator 262 includes a piston 268a formed with or fixed to arod 268 and disposed in a cylinder defined by rear housing member 40, anend plate 269 for closing the cylinder, and the shift fork 266 fixed torod 268. Hydraulic sealing of the piston and cylinder is provided byseals in a conventional manner. Passages 270 and 272 provide means forporting oil to and from the actuator via the unshown control system.

OPERATION

In reviewing the operation, it will be assumed that transmission 10 isinstalled in a land vehicle having an internal combustion engine coupleddirectly to shroud 64 of the torque converter, and that a shift controlsystem will automatically effect shifting to the desired speed ratios inthe proper sequence. Such control systems are well known and are oftenmade responsive to parameters such as engine load and vehicle speed. Itwill also be assumed that the shift control system includes a shiftcontrol selector which is selectively placed in a neutral position todisengage the transmission, in a drive position to effect forwardmovement of the vehicle, and in a reverse position to effect reversemovement of the vehicle. However, the shift control selector could havefour forward drive positions corresponding to the four forward speedratios of the transmission; in which case, the shift control systemcould be made operative to engage only the ratio corresponding to theselector position or sequentially upshift and downshift between the lowspeed ratio and the highest ratio corresponding to the position of theselector. The shift control systems referred to herein are by way ofexample only and do not form part of the invention herein nor are theypurported to be preferred forms of shift control systems.

In the following operational description, friction clutch 82 and 84 willbe referred to as being either fully engaged or momentarily engaged.When fully engaged, the clutch locks-up. When momentarily engaged, theclutch slips. To implement the slipping, the control system pressure forengaging the clutch may be reduced and/or supplied for such a shortperiod that full engagement or lock-up is not reached.

With the shift control lever in neutral and the engine running, inputshaft 16 is driven by torque converter assembly 14; countershafts 24 and26 are driven at a speed proportional to the speed of input shaft 16 viagears 16a and 78; ratio gears 86, 170, and 172 are driven at speedsproportional to their respective countershaft gears 246, 248 and 250;and the control system ports pressurized oil to chambers 220 and 222 ofhydraulic actuator 204 to position rod 214 in the neutral position asshown in the drawings. Further, output shaft 20 is completelydisconnected from input shaft 16 and countershafts 24 and 26 sincefriction clutches 82 and 84, blocker-clutch assembly 30, and positiveclutch 260 are all disengaged.

Assume now that a vehicle operator places the shift control lever in thedrive position and wishes to accelerate the vehicle in a forwarddirection to a speed which will cause the control system to sequentiallypower upshift through each of the four forward drive ratios of thetransmission. When the shift lever is placed in drive, the controlsystem fully engages friction clutch 84 by porting pressurized oil tochamber 140 thereby squeezing friction disks 134 and 136 together andconnecting gear 86 to output shaft 20 via housings 130 and 88 ofclutches 84 and 82, respectively.

When the sensed parameters indicate upshifting from the low speed ratio,the control system will operate to effect a power upshift from the lowspeed ratio provided by gear 86 to the first intermediate speed ratioprovided by gear 170. To wit, the control system simultaneously portschamber 140 to return to disconnect gear 86 from shaft 20, portspressurized oil to chamber 96 to momentarily engage clutch 82 andconnect input shaft 16 directly to output shaft 20 for bringing gear 170toward synchronism with shaft 20, and continues to port pressurized oilto chamber 222 of hydraulic actuator 204 while porting chamber 220 ofthe actuator to return to move rod 214 leftward. The rate of oilpressure buildup and release in chambers 96 and 140, respectively, iscontrolled to effect a smooth transition of driving torque from clutchmechanism 84 to clutch mechanism 82. While the driving torque throughclutch mechanisms 82 and 84 is increasing and decreasing, respectively,the pressurized oil in chamber 222 acts on distal side 215b of piston215 and moves piston 215, rod 214, spacer 217, and piston 216 leftwardtoward contact with end wall 210 by piston 216. Initial movement of rod214 is transmitted to flange portion 186b of blocker-clutch assembly 30via coil spring 244 of spring box 206. This initial movement resilientlymoves friction clutch member 190 into engagement with friction clutchmember 170a via leaf springs 202 and the chamfered shoulders of splitpins 196. During normal operating conditions, friction clutch members190 and 170a will engage before clutch mechanism 82 can bring shaft 20into synchronism with gear 170. Hence, the reduced diameter portion ofpins 188 will move to one side of holes 186c and shoulders 186e and 188cwill engage and block engagement of jaw clutch member 186 with jawclutch member 170a. The blocking action of shoulders 186e and 188carrests further movement of shift fork 230a and sleeve 230. However,piston rod 214 continues to move leftward until piston 216 contacts endwall 210, thereby compressing coil spring 244 of spring box 206 andresiliently loading square shoulders 186e against blocking shoulders188c. The blocking action of shoulders 186e and 188c continues untilclutch 82 causes gear 170 to cross synchronism with shaft 20. Assynchronism is crossed, pins 188 move into axial alignment with holes186c, thereby allowing the compressed force of spring 244 to quicklymove or snap sleeve 230, shift fork 230a, and flange portion 186 bleftward and carry jaw clutch member 186 into engagement with jaw clutchmember 170a. While the jaw clutch members are engaging, the controlsystem effects an unrestricted porting of chamber 96 to return toquickly disengage clutch mechanism 82. The signal to effect a timelyporting of chamber 96 to return may be provided by an unshown positionindicator which senses the leftward movement of either sleeve 230, fork230a, flange 186b, or jaw clutch member 186. Position indicators of thistype are well known in the art.

The blocker-clutch and spring box arrangement enhances the transmissioncontrol and operation in several ways. For example, since the force forshifting jaw clutch member 186 is resiliently stored in coil spring 244of the spring box, control system timing for porting fluid to actuator204 need not be as precise as it would need be if the actuator weremoving the jaw clutch member directly. Since the force for shifting thejaw clutch member is resiliently stored in the coil spring, the pressureof the oil ported to the actuator need not be precisely controlled.Further, since only sleeve 230 and shift fork 230a move to engage thejaw clutch member when synchronism is reached, the mass of the movingparts is reduced, whereby the jaw clutch member is moved faster with agiven force and whereby impulse forces are maintained relatively low.

When the sensed parameters indicate upshifting from the firstintermediate speed ratio, the control system will operate to effect apower upshift from the first intermediate speed ratio provided by gear170 to the second intermediate speed ratio provided by gear 172. Toeffect the power shift out of the first intermediate speed ratio, torqueon the splines of jaw clutch members 170a and 186 must be relieved. Whenthe engine is driving the vehicle wheels, the torque (hereinafter called"driving torque") is relieved by momentarily engaging friction clutch82. However, when the wheels are driving the engine, the torque(hereinafter called "coast mode torque") is merely increased bymomentarily actuating friction clutch 82. To relieve the coast modetorque, the control system may be programmed to always momentarilyengage friction clutch 84 prior to momentary engagement of frictionclutch 82 or to only momentarily engage friction clutch 84 prior tomomentary engagement of friction clutch 82 when the engine power controlis less than a predetermined amount, e.g., a 20 percent power position.To effect the shift, the control system simultaneously ports chamber 222of actuator 204 to return, ports pressurized oil to chamber 218 to applya rightward force on flange portion 186b via spring 244 of the springbox, momentarily ports pressurized oil to chamber 140 of friction clutch84 to relieve coast mode torque, and then momentarily ports pressurizedoil to chamber 96 of friction clutch 82 while porting chamber 140 toreturn. Momentary engagement of clutch 82 relieves any driving torqueand allows disengagement of jaw clutch member 186 from jaw clutch member170a and then brings the speed of gear 172 down to synchronism withoutput shaft 20. While clutches 82 and 84 are relieving the torque onthe splines of the jaw clutch members, the pressurized oil in chambercontinues to act on mutually facing side 215a of piston 215, therebymoving rod 214 rightward until piston 215 contacts shoulder 208g. Theinitial rightward movement of rod 214 compresses coil spring 244 andapplies a shifting force which snaps jaw clutch member rightward out ofengagement with jaw clutch 170a in response to clutches 82 and 84relieving the torque on the splines. As flange portion 186b movesrightward, it passes through neutral and the chamfered shoulders ofsplit pins 196 engage the chamfered shoulders of holes 186d, therebyeffecting a resilient engagement of friction clutch member 192 withfriction clutch member 194 via the force of spring 202.

During normal operating conditions, friction clutch members 192 and 194will engage before clutch mechanism 82 can bring shaft 20 intosynchronism with gear 172. Hence, the reduced diameter portion of pins188 will move to one side of holes 186c and shoulders 186f and 188d willengage and block engagement of jaw clutch member 186 with jaw clutchmember 172a. The blocking action of shoulders 186f and 188d arrestsfurther rightward movement of shift fork 230a and sleeve 230. However,piston rod 214 is free to continue its rightward movement until piston215 contacts shoulder 208g, thereby compressing coil spring 244 ofspring box 206 and resiliently loading square shoulders 186f againstblocking shoulders 188d. The blocking action of shoulders 186f and 188dcontinues until clutch 82 brings gear 172 across synchronism with shaft20. As synchronism is crossed, pins 188 move into axial alignment withholes 186c, thereby allowing the compressed force of spring 244 toquickly snap jaw clutch member 186 into engagement with jaw clutchmember 172a. While the jaw clutch members are engaging, the controlsystem effects an unrestricted porting of chamber 96 to return toquickly disengage clutch mechanism 82. The signal to effect a timelyporting of chamber 96 to return may be provided by the unshown positionindicator previously mentioned.

When the sensed parameters indicate upshifting from the secondintermediate speed ratio, the control system will operate to effect apower upshift from the second intermediate speed ratio provided by gear172 to the high or direct drive ratio provided by connecting input shaft16 directly to output shaft 20 via clutch mechanism 82. To wit, thecontrol system simultaneously ports pressurized oil to chambers 220 and222 of actuator 204, ports chamber 218 of the actuator to return,momentarily ports pressurized oil to chamber 140 to relieve coast modetorque, and then ports pressurized oil to chamber 96 to fully engageclutch mechanism 82 and relieve any driving torque while porting chamber140 to return. While clutches 82 and 84 are relieving the torque on thesplines of jaw clutch members 186 and 172a, the pressurized oil inchambers 220 and 222 acts on the distal sides of pistons 216 and 215 andmoves 216 rightward to its neutral position against the stop defined byshoulder 208f and moves piston 215 leftward to its neutral positionagainst the stop defined by sleeve 217. Further leftward movement ofpiston 215 and rod 214 is arrested since the area of distal side 216b ofpiston 216 is greater than the area of distal side 215b of piston 215.The initial leftward movement of rod 214 begins to compress coil spring244 of spring box 206 and thereby applies an increasing shifting forceto flange 186b for snapping jaw clutch member 186 leftward out ofengagement with jaw clutch member 172a when the torque on the splines ofjaw clutch members 186 and 172a is relieved by clutches 82 and 84.

Assuming now that the sensed parameters indicate downshifting from thehigh speed ratio, the control will operate to effect a power downshiftfrom the high speed ratio provided by friction clutch 82 to the secondintermediate speed ratio provided by gear 172. To wit, the controlsystem simultaneously ports chamber 96 of clutch 82 to return, portspressurized oil to chamber 140 of clutch 86 to momentarily connectoutput shaft 20 to the countershaft via the low speed ratio gear tobring gear 172 up toward synchronism with output shaft 20, portspressurized oil to chamber 218 of hydraulic actuator 204, and portschamber 222 of the actuator to return. As described with respect toupshifting, the rate of oil flow to and from chambers 140 and 96,respectively, is controlled to effect a smooth transition of drivingtorque from clutch mechanism 82 to clutch mechanism 84. While thedriving torque through clutch mechanisms 84 and 82 is increasing anddecreasing, respectively, the pressurized oil in chamber 218 acts onmutually facing side 215a of piston 215 and moves piston 215 and rod 214rightward toward contact with shoulder 208g. Initial movement of rod 214is transmitted to flange portion 186b of blocker-clutch assembly 30 viacoil spring 244 of spring box 206. This initial movement resilientlymoves friction clutch member 192 into engagement with friction clutchmember 194 via leaf spring 202 and the chamfered shoulders of split pins196. During normal operating conditions, friction clutch members 192 and194 will engage before clutch mechanism 84 can bring gear 172 up tosynchronism with shaft 20. Hence, the reduced diameter portion of pins188 will move to one side of holes 186c and shoulders 186f and 188d willengage and block engagement of jaw clutch member 186 with jaw clutchmember 172a. The blocking action of shoulders 186f and 188d arrestsfurther movement of shift fork 230a and sleeve 230. However, piston rod214 continues to move rightward until piston 215 contacts shoulder 208g,thereby compressing coil spring 244 of spring box 206 and resilientlyloading square shoulders 186f against blocking shoulders 188d. Theblocking action of shoulders 186f and 188d continues until clutch 84causes gear 172 to cross synchronism with shaft 20. As synchronism iscrossed, pins 188 move into axial alignment with holes 186c, therebyallowing the compressed force of spring 244 to quickly snap jaw clutchmember 186 leftward into engagement with jaw clutch member 172a. Whilethe jaw clutch members are engaging, the control system effects anunrestricted porting of chamber 140 to return to quickly disengageclutch mechanism 84. The signal to effect the timely porting of chamber140 to return may be provided by the unshown position indicatorpreviously mentioned during the upshifting description.

When the sensed parameters indicate downshifting from the secondintermediate speed ratio, the control system will operate to effect apower downshift from the second intermediate speed ratio provided bygear 172 to the first intermediate speed ratio provided by gear 170. Asin upshifting, driving and coast mode torque on the splines must berelieved. To effect the shift and relieve the torque, the control systemcontinues to port pressurized oil to chamber 220 of actuator 204, portschamber 222 of the actuator to return, momentarily ports pressurized oilto chamber 96 to relieve driving torque on the splines of jaw clutchmembers 186 and 172a, and then momentarily ports pressurized oil tochamber 140 of friction clutch 84 (while porting chamber 96 to return)to relieve any coast mode torque and to bring the speed of gear 170 upto synchronism with output shaft 20 after jaw clutch member 186disengages from jaw clutch member 172a. Further operation to completethe shift is analogous to the operation previously described.

When the sensed parameters indicate downshifting from the firstintermediate speed ratio, the control system will operate to effect apower downshift from the first intermediate speed ratio provided by gear170 to the low speed ratio provided by fully engaging friction clutch84. To effect the shift and relieve the torque on the splines of jawclutch member 186 and 170a, the control system ports pressurized oil tochamber 222 of actuator 204, ports chamber 220 to return, momentarilyports pressurized oil to chamber 96 to relieve driving torque on thesplines, and then ports pressurized oil to chamber 140 to fully engagefriction clutch 84 (while porting chamber 96 to return) to relieve anycoast mode torque. Further operation to complete the shift is analogousto the operation previously described.

DESCRIPTION OF FIG. 6

Looking now at FIG. 6, therein is shown an alternative embodiment of thetransmission torque converter and input shaft which provides thetransmission with an automatic torque converter bypass when thetransmission is in the direct or the fourth speed drive ratio. Indescribing the embodiment of FIG. 6, elements therein which areidentical to elements in FIGS. 1-5 will have the same reference numeralsbut suffixed with a prime. The alternative embodiment includes a torqueconverter assembly 300 disposed in bell housing portion 38a', a sleeveshaft or torque converter driven shaft 302 rotatably supported in fronthousing member 38' by bearing 44', and a bypass shaft 304 rotatablysupported within sleeve shaft 302.

The torque converter assembly 300 includes an impeller 306 driven by ashroud 308, a turbine 310 hydraulically driven by the impeller and inturn drivingly fixed to sleeve shaft 302 at 312, and a runner or stator314 which becomes grounded to housing member 38' via a one-way rollerclutch 316 carried by a sleeve 318 fixed to the housing member. The rearside of shroud 308 is fixed to a sleeve 320 which rotatably supports therear of the shroud and drives a pump 322. Pump 322 may be a well knowncrescent gear pump for pressurizing the torque converter, forlubricating the transmission, and for providing pressurized oil toengage friction clutches and actuators in the transmission. The frontside of shroud 308 includes a cup-shaped portion 308a having internalsplines 308b.

Torque converter driven shaft 302 is integrally formed with a gear 302aanalogous to gear 16a and in constant mesh with countershaft gear 78',whereby countershaft assembly is driven by the torque converter as inFIGS. 1-5. Bypass shaft 304 is drivingly connected to shroud 308 viasplines 308b and is integrally formed with an annular flange portion304a having external splines 304b analogous to splines 16d for drivingthe friction disks of the direct drive clutch mechanism, and a recess304c carrying bearing 80' for rotatably supporting the front end of theoutput shaft, not shown in FIG. 6. Hence, engagement of clutch mechanism82' automatically bypasses the torque converter with its inherentinefficiency and negates the need for a separate torque converter bypassclutch which would add to the size and weight and complexity of thetransmission and its control system.

The preferred embodiments of the invention have been disclosed forillustrative purposes. Many variations and modifications of thepreferred embodiment are believed to be within the spirit of theinvention. For example, the blocker-clutch assembly 30 may be replacedwith blocker-clutch assemblies such as disclosed in U.S. Pat. No. Re.29,601; U.S. Pat. Nos. 3,910,131; and 3,983,979 which are incorporatedherein by reference. Also, the power downshift arrangement may bedispensed with in favor of driver manipulation of engine speed torelieve torque on the splines of the jaw clutch members and providesynchronism therebetween. The following claims are intended to cover theinventive portions of the preferred embodiment and variations andmodifications within the spirit of the invention.

What is claimed is:
 1. In a transmission of the type including ahousing; an input shaft and an output shaft mounted for rotation in thehousing; a countershaft mounted for rotation in the housing and disposedparallel to the other shafts; and ratio change means connectable betweensaid input and output shafts to provide at least low, intermediate andhigh speed ratio changes between the input and output shafts; theimprovement wherein the ratio change means comprises:low andintermediate speed ratio gears mounted for rotation about one of saidshafts and operative when coupled to said one shaft to provide said lowand intermediate speed ratios between said input and output shafts viasaid countershaft; first and second jaw clutch members operative whenengaged to couple said intermediate gear to said one shaft, said membersnormally rotating at different speeds during transmission upshifting anddownshifting into said intermediate gear; a first friction clutchoperative when engaged to frictionally interconnect said input andoutput shafts, said first friction clutch fully engageable to couplesaid low speed ratio gear directly to said one shaft and momentarilyengageable during downshifting into said intermediate speed ratio tomomentarily connect said low speed ratio gear directly to said one shaftto synchronize said members for engagement; and a second friction clutchoperative when engaged to frictionally interconnect said input andoutput shafts, said second friction clutch fully engageable to couplesaid input shaft directly to said output shaft to provide said highspeed ratio and momentarily engageable during upshifting into saidintermediate speed ratio to momentarily connect said input shaftdirectly to said output shaft to synchronize said members forengagement, and said first and second friction clutches being disengagedwhen said input and output shafts are interconnected by saidintermediate speed ratio.
 2. The improvement of claim 1, wherein saidcountershaft is in constant driving relation with said input shaft; andsaid low and intermediate speed ratio gears are mounted for rotationabout said output shaft.
 3. The improvement of claim 1 or 2, whereinsaid second friction clutch includes a housing member fixed for rotationwith said output shaft and a set of friction disks alternately splinedto said input shaft and said housing member and operative when squeezedtogether to frictionally connect said input shaft to said output shaftvia said housing member; and said first friction clutch includes ahousing member fixed for rotation with said low speed ratio gear andmounted for rotation about said output shaft, and a set of frictiondisks alternately splined to said housing members and operative whensqueezed together to frictionally connect said low speed ratio gear tosaid output shaft via said housing members.
 4. In a powershifttransmission of the type including a housing; an input shaft, an outputshaft, and at least one countershaft; at least low, intermediate, andhigh speed ratios means associated with the shafts and selectivelyconnectable between the input and output shafts; the improvementcomprising:a jaw clutch means associated with the intermediate speedratio and operative when engaged to interconnect the input and outputshafts via the intermediate speed ratio means; a first friction clutchassociated with the low speed ratio means, said first friction clutchfully engageable to interconnect the input and output shafts via the lowspeed ratio, and said first friction clutch momentarily engageableduring downshifting into the intermediate speed ratio to momentarilyconnect said low speed ratio gear directly to said one shaft tosynchronize said members for engagement; and a second friction clutchassociated with the high speed ratio means, said second friction clutchfully engageable to interconnect the input and output shafts via thehigh speed ratio means, said second friction clutch momentarilyengageable during upshifting into the intermediate speed ratio topartially connect said input shaft directly to said output shaft tosynchronize said jaw clutch for engagement, and said first and secondfriction clutches being disengaged when said input and output shafts areinterconnected by said intermediate speed ratio.
 5. A powershifttransmission comprising:a housing; input drive means, an output shaft,and at least one countershaft mounted for rotation in said housing, saidcountershaft in constant driving relation with said input drive means;low and intermediate speed ratio means, each ratio means including agear pair in constant mesh, one gear of each pair permanently fixed toone of said shafts and the other gear of each pair rotatably mounted onsaid other shaft; a jaw clutch means operative when engaged to connectsaid rotatably mounted intermediate speed ratio gear to said othershaft; a first friction clutch operative when engaged to connect saidrotatably mounted low speed ratio gear to said other shaft independentof said intermediate speed ratio gear pair and said jaw clutch; a secondfriction clutch operative when engaged to interconnect said input drivemeans with said output shaft for providing a high speed ratioindependent of said other speed ratio means and said other clutches, andsaid first and second friction clutches being disengaged when said jawclutch means is engaged.
 6. A powershift transmission comprising:ahousing; input drive means, an output shaft, and at least onecountershaft mounted for rotation in said housing, said countershaft inconstant driving relation with said input drive means; low, and firstand second intermediate speed ratio means, each ratio means including agear pair in constant mesh, one gear of each pair permanently fixed toone of said shafts and the other gear of each pair rotatably mounted onsaid other shaft; jaw clutch means disposed between said rotatablymounted first and second intermediate speed ratio gears for selectivelyconnecting said rotatably mounted first and second intermediate ratiogears to said other shaft; a first friction clutch operative whenengaged to connect said rotatably mounted low speed ratio gear to saidother shaft independent of said first and second intermediate speedratio gear pairs and said jaw clutch means; and a second friction clutchoperative when engaged to interconnect said input drive means with saidoutput shaft for providing a high speed ratio independent of said otherspeed ratio gear pairs and said other clutches, and said first andsecond friction clutches being disengaged when said jaw clutch meansconnects either of said rotatably mounted first and second intermediateratio gears to said other shaft.
 7. The improvement of claim 4, 5, or 6,wherein said jaw clutch includes:blocker means for preventingasynchronous engagement of the jaw clutch means.
 8. The transmission ofclaim 5 or 6, wherein said input drive means includes:a fluid couplinghaving an input directly connectable to a source of power and an outputin constant driving relation with said countershaft; and a bypass shafthaving an input directly connectable to said source of power and anoutput connectable to said output shaft via said second friction clutchto provide said high-speed ratio.
 9. The transmission of claim 5 or 6,wherein said first friction clutch is momentarily engagable duringdownshifting into said intermediate speed ratio to synchronize said jawclutch means for engagement, said second friction clutch is momentarilyengagable during upshifting into said intermediate speed ratio tosynchronize said jaw clutch means for engagement, and furtherincluding:blocker means for preventing asynchronous engagement of saidjaw clutch means.
 10. The transmission of claim 9, wherein said inputdrive means includes:a fluid coupling having an input directlyconnectable to a source of power and an output in said constant drivingrelation with said countershaft; and a bypass shaft having an inputdirectly connectable to said source of power and an output connectableto said output shaft via said second friction clutch to provide saidhigh-speed ratio.